gistfile1.py

>>> np.__version__
'1.8.1'
>>> ar = np.ma.array([1, 1, 1, np.ma.masked, 1, 1, 1])
>>> ar
masked_array(data = [1.0 1.0 1.0 -- 1.0 1.0 1.0],
             mask = [False False False  True False False False],
       fill_value = 1e+20)

>>> np.gradient(ar)
masked_array(data = [0.0 0.0 -- 0.0 -- 0.0 0.0],
             mask = [False False  True False  True False False],
       fill_value = 1e+20)

>>> ar
masked_array(data = [1.0 1.0 -- nan -- 1.0 1.0],
             mask = [False False  True False  True False False],
       fill_value = 1e+20)